ObjectiveBased on the inhibitory activity of phosphodiesterase （PDE）， a method for determining the anti-inflammatory activity of Qingjin Huatantang was established to supplement and improve the quality control system of this famous classical formula. MethodHigh performance liquid chromatography （HPLC） was used to determine the activity of PDE， and the dose-effect relationship of inhibiting PDE activity of Qingjin Huatantang was investigated. The mobile phase consisted of methanol-0.5% acetic acid aqueous solution （5∶95）， and the detection wavelength was 254 nm. By measuring the PDE inhibition rate of multiple batches of Qingjin Huatantang water extract lyophilized powder， biological activity was marked with the activity of the neutralizing enzyme in the international unit U. ResultWhen the concentration of reaction substrate （cyclic adenosine monophosphate） was 50 μmol·L^-1 and the reaction time was 60 min， the enzymatic reaction was stable with 4 U·mL^-1 of PDE. In this reaction system， when the concentration of Qingjin Huatantang water extract lyophilized powder was 0.11-3.0 g·L^-1， the inhibitory effect of PDE showed a concentration-dependent relationship. It was determined that the concentration of Qingjin Huatantang water extract lyophilized powder to be tested was 1 g·L^-1， which showed a significant and stable inhibitory effect on PDE， and the inhibitory rate was >45%， that is， 1 mg of Qingjin Huatantang water extract lyophilized powder could neutralize the activity of 1.8 U PDE at least. ConclusionThis study establishes a biological activity evaluation method of Qingjin Huatantang based on the inhibitory activity of PDE， and the anti-inflammatory activity of Qingjin Huatantang is characterized by international unit U of PDE activity， which can provide a new method for the determination of biological activity of traditional Chinese medicine compounds.